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Joel Greenblatt: Source-Scoped Study Note
Screening rules and portfolio claims. An editorial study assignment with explicit source limits, not a hidden rulebook.
What the source can support
The operator identifies Magic Formula Investing with the strategy described in The Little Book That Beats the Market and warns that the formula does not guarantee success.
Original exercise for this learning question
Separate a screening output from a portfolio return. Record the selected universe, observation date and missing implementation assumptions. Explain why an ordered candidate list alone cannot establish transaction costs or an achieved account result.
Work without a live account. Record the original reference, the observation boundary and the first answer before examining a later result. When a definition is unclear, mark the uncertainty; do not supply a favourable fact from hindsight or attribute your own invented parameter to the author.
The distinction to explain
An educational screener comparison is not personalised portfolio advice or evidence of future performance.
Artifact and transfer review
Universe, source date, selection output and unobserved portfolio implementation.
Retain the baseline and correction as separate artifacts. For a fresh task, explain what was supplied, what you assumed and what remains unobserved. This review concerns your understanding of an evidence boundary, not the original trader's current performance or a reproduction of a private system.
Source Identity
Original operator, author or publisher reference
The scope above identifies whether the reference is an authored resource, provider interpretation, institutional description or catalogue identity. It does not imply paid access, a new account audit or a complete modern method.
Public notes versus private courses / Observation before hindsight / Study library
Learning Concepts and Fresh Cases
A ranking screen needs definitions for its fields and a declared universe. A ratio name alone cannot tell another reader which accounting period, denominator or exclusions were used. A ranked list is a research output, not automatically a portfolio or a recommendation.
Create three fictional companies and rank them under a declared classroom definition. Remove one essential denominator and explain what happens to that observation. Compare the effect of a reasonable alternate convention without choosing the convention that makes a favoured company rank first.
Keep earnings yield, return on capital, rebalancing and special situations as reading topics. The original website supplies a source boundary, not proof that this reader replicated a strategy outcome. The artifact should retain field definitions, unavailable records and a distinction between a source-defined screen and your own adaptation.
Retained Vocabulary Reading Trail
Magic Formula, earnings yield, return on capital, quantitative value investing, systematic rebalancing, special situations.
This vocabulary preserves the earlier topic coverage. It is a list of research leads, not a verified private rulebook. Any numerical setting or author-specific parameter needs its original definition and scope before being used or attributed.